# big formula with description

It is possible to make the following thing, helping you Latex...?

An option using the tikzmark library:

The code:

\documentclass{article}
\usepackage{xparse}
\usepackage{tikz}
\usetikzlibrary{tikzmark}
\usepackage{amsmath}

\NewDocumentCommand\MyInfo{O{(0,0)}O{}mmm}{
\begin{tikzpicture}[remember picture,overlay,#2]
\node[pin=#4:{\parbox{5cm}{\raggedright #5}}] at ([shift={#1}]pic cs:#3) {};
\end{tikzpicture}%
}

\begin{document}

$\LARGE \underbrace{\tikzmark{i}\int_{\tikzmark{a}a}^{\tikzmark{b}b} f(\tikzmark{f}x)\textrm{d}\tikzmark{x}x}_{\text{\normalsize Integral of f from a to b}\tikzmark{bii}}$

\MyInfo{a}{220}{Lower limit  of integration}
\MyInfo[(0,9pt)]{b}{140}{Upper limit  of integration}
\MyInfo[(10pt,6pt)]{x}{40}{$x$ is the variable of integration}
\MyInfo[(2pt,18pt)][pin distance=1.5cm]{f}{90}{The function is the integrand}
\MyInfo[(0pt,3pt)]{bii}{0}{When you find the value \\ of the integral, \\ you have evaluated the integral}

\end{document}

The code needs three runs to stabilize.

Just a template with PSTricks. The remaining trivial parts are intentionally left as your exercise.

\documentclass[preview,border=12pt,12pt]{standalone}
\usepackage{pst-node}
\usepackage{amsmath}

\newsavebox\IBox
\savebox\IBox{\psscalebox{2}{\raisebox{\depth}[\totalheight]{$\underbrace{\rnode[l]{int}{\displaystyle\int_{\rnode[bl]{a}{a}}^{\rnode[tl]{b}{b}}}\quad f(x)\quad \mathrm{d}x}_{\text{\tiny Integral of$f$from$a$to$b$}}$}}}

\psset
{
xunit=0.2\wd\IBox,
yunit=0.2\ht\IBox,
}
\begin{document}

\pspicture[showgrid=false](-\wd\IBox,-\ht\IBox)(\wd\IBox,\ht\IBox)
\rput(0,0){\usebox\IBox}
\rput(-2,4){\rnode[b]{bnote}{Upper limit of integration}}
\ncline{bnote}{b}
\endpspicture
\end{document}

• It needs only one compilation to converge to the correct output. – kiss my armpit Aug 3 '14 at 18:04